The present invention relates to a drive unit and a manufacturing method of the drive unit.
A drive unit including a rotating electrical machine (a motor and a generator) is provided with a rotation sensor for precisely detecting a rotational position of a rotor with respect to a stator in order to provide accurate speed control of the rotating electrical machine. The rotational position of the rotor is precisely detected by the rotation sensor in order to determine a current value and a current phase that are to be applied to the rotating electrical machine based on an output signal from the rotation sensor.
It is extremely rare that such a drive unit is assembled without any assembly error between the rotating electrical machine and the rotation sensor with a single assembling operation. Such an assembly error or the like causes a phase difference between the rotating electrical machine and the rotation sensor. The “phase difference between the rotating electrical machine and the rotation sensor” herein means the phase difference between a rotational phase of a specific part in a circumferential direction of the rotor of the rotating electrical machine and a rotational phase of a part of the rotation sensor corresponding to the specific part (the same applies to the description given below). In order to make these phases match each other, it is usually necessary to adjust this phase difference at least once.
Japanese Patent Application Publication No. JP-A-2005-295639 describes a method for adjusting the phase difference between the rotating electrical machine and the rotation sensor. After the rotating electrical machine and the rotation sensor are assembled together, a counter electromotive force is generated by rotating a rotating shaft of the rotating electrical machine, and a voltage waveform of the rotating electrical machine is compared with a detecting voltage waveform of the rotation sensor. When the phase difference between the voltage waveforms is out of a predetermined range, the rotation sensor is manually rotated in a circumferential direction with respect to the rotating electrical machine. In this method, the above operation is repeated until the phase difference falls within the predetermined range. Japanese Patent Application Publication No. JP-A-S61-10715 describes a method in which an error of the rotation sensor is measured in advance and stored in a memory portion of a control device for controlling the rotation sensor, and an accurate position is obtained based on the stored error information and a detected value obtained from the rotation sensor.